Methods of three-dimensional electrophoretic deposition for ceramic and cermet applications and systems thereof

ABSTRACT

A product according to one embodiment includes a first layer comprising a first material, the first layer having a gradient in composition, microstructure and/or density in an x-y plane, and the x-y plane being oriented parallel to a plane of deposition of the first layer. The first material includes non-spherical particles; and the product is optically transparent. A ceramic according to another embodiment includes a plurality of layers comprising non-spherical particles of a non-cubic material. Each layer is individually characterized by the non-spherical particles thereof being aligned in a common direction. A product in another embodiment includes a first layer having a first composition, a first microstructure, and a first density; and a second layer above the first layer, the second layer having: a second composition, a second microstructure, and/or a second density. A gradient in composition, microstructure, and/or density exists between the first layer and the second layer.

The United States Government has rights in this invention pursuant toContract No. DE-AC52-07NA27344 between the United States Department ofEnergy and Lawrence Livermore National Security, LLC for the operationof Lawrence Livermore National Laboratory.

FIELD OF THE INVENTION

The present invention relates to functionality graded materials, andmore particularly, to using three-dimensional electrophoretic depositionto form functionality graded materials.

BACKGROUND

The electrophoretic deposition (EPD) process utilizes electric fields todeposit charged nanoparticles from a solution onto a substrate. Earlierindustrial use of the EPD process employed organic solvent solutions andtherefore typically generated hazardous waste as a by-product of theprocess. In addition, the shapes, compositions, densities, andmicrostructures of materials formed through EPD processes have typicallybeen difficult if not impossible to control, either separately or incombination with one another. Also, it is extremely difficult to formstructures from more than one material. That is to say, typical EPDprocesses are limited in that they are only capable of forming planar,homogenous structures.

SUMMARY

A product according to one embodiment includes a first layer comprisinga first material, the first layer having a gradient in composition,microstructure and/or density in an x-y plane, and the x-y plane beingoriented parallel to a plane of deposition of the first layer. The firstmaterial includes non-spherical particles; and the product is opticallytransparent.

A ceramic according to another embodiment includes a plurality of layerscomprising non-spherical particles of a non-cubic material. Each layeris individually characterized by the non-spherical particles thereofbeing aligned in a common direction.

A product in yet another embodiment includes a first layer having afirst composition, a first microstructure, and a first density; and asecond layer above the first layer, the second layer having: a secondcomposition, a second microstructure, and/or a second density. Agradient in composition, microstructure, and/or density exists betweenthe first layer and the second layer.

Other aspects and embodiments of the present invention will becomeapparent from the following detailed description, which, when taken inconjunction with the drawings, illustrate by way of example theprinciples of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified schematic diagram of an electrophoreticdeposition (EPD) device, according to one embodiment.

FIGS. 2A-2C show a simplified view of layers of a structure formedthrough an EPD process, according to one embodiment.

FIG. 3A is a simplified schematic diagram of an EPD device, according toone embodiment.

FIG. 3B is a simplified schematic diagram of an EPD device, according toone embodiment.

FIG. 4 is a flow diagram of a method for forming a ceramic, metal, orcermet through electrophoretic deposition, according to one embodiment.

FIGS. 5A-5B show the formation of a ceramic through EPD, according toone embodiment.

FIG. 6 is a simplified schematic diagram of an EPD device, according toone embodiment.

FIG. 7 is a flow diagram of a method for forming a ceramic, metal, orcermet through electrophoretic deposition, according to one embodiment.

FIGS. 8A-8C show electrode configurations for EPD, according to variousembodiments.

DETAILED DESCRIPTION

The following description is made for the purpose of illustrating thegeneral principles of the present invention and is not meant to limitthe inventive concepts claimed herein. Further, particular featuresdescribed herein can be used in combination with other describedfeatures in each of the various possible combinations and permutations.

Unless otherwise specifically defined herein, all terms are to be giventheir broadest possible interpretation including meanings implied fromthe specification as well as meanings understood by those skilled in theart and/or as defined in dictionaries, treatises, etc.

It must also be noted that, as used in the specification and theappended claims, the singular forms “a,” “an,” and “the” include pluralreferents unless otherwise specified.

Functionally graded materials (FGM) fabricated with gradients incomposition, microstructure, and/or density produce enhanced bulkproperties, which typically correspond to a combination of the precursormaterial properties. For example, controlled composite layers of boroncarbide and aluminum may produce lightweight ceramic materials that areboth hard and ductile for improved armor. Current graded materials areprimarily produced by coarse, layered processing techniques ormelt-based approaches which are typically limited to abrupt gradients incomposition along one axis only. The techniques described hereinovercome these limitations using electrophoretic deposition (EPD)technology to fabricate functionally graded, nanostructured materialstailored in three-dimensions.

Typically, EPD has been used for forming coatings on surfaces usingorganic solvents. Recent nanomaterial work has demonstrated thatelectrophoretic deposition (EPD) is capable of, at small length scales,being performed using aqueous (water-based) solutions. In addition, EPDmay be performed using a wide variety of charged nanoparticles, such asoxides, metals, polymers, semiconductors, diamond, etc.

In one general embodiment, a ceramic, metal, or cermet includes a firstlayer having a gradient in composition, microstructure and/or density inan x-y plane oriented parallel to a plane of deposition of the firstlayer.

In another general embodiment, a method for forming a ceramic, metal, orcermet includes providing light in a first pattern to a photoconductivelayer positioned near a transparent or semi-transparent electrode of anelectrophoretic deposition (EPD) chamber, wherein the photoconductivelayer is between the transparent or semi-transparent electrode and asecond electrode, wherein portions of the photoconductive layer becomeconductive in response to the light according to the first pattern,applying a voltage difference across the transparent or semi-transparentelectrode and the second electrode, and electrophoretically depositing afirst material above the photoconductive layer according to the firstpattern, wherein the EPD chamber comprises an aqueous or organicsolution having the first material to be deposited therein.

According to another general embodiment, a ceramic includes a pluralityof layers comprising particles of a non-cubic material, wherein eachlayer is characterized by the particles of the non-cubic material beingaligned in a common direction.

In yet another general embodiment, a method for forming a ceramicincludes electrophoretically depositing a plurality of layers ofparticles of a non-cubic material, wherein the particles of thedeposited non-cubic material are oriented in a common direction.

In another general embodiment, a ceramic, metal, or cermet includes afirst layer having a first composition, a first microstructure, and afirst density, and a second layer above the first layer, the secondlayer having at least one of: a second composition, a secondmicrostructure, and a second density, wherein a gradient exists betweenthe first layer and the second layer and the first and second layershave a characteristic of being formed in an EPD chamber.

According to another general embodiment, a method for forming a ceramic,metal, or cermet includes providing an EPD device which includes an EPDchamber, a first electrode positioned at an end of the EPD chamber, anda second electrode positioned at an opposite end of the EPD chamber,providing a first solution to the EPD chamber using an automatedinjection system, the first solution comprising a first solvent and afirst material, applying a voltage difference across the first electrodeand the second electrode, electrophoretically depositing the firstmaterial above the first electrode to form a first layer, wherein thefirst layer has a first composition, a first microstructure, and a firstdensity, introducing a second solution to the EPD chamber using theautomated injection system, the second solution comprising a secondsolvent and a second material, applying a voltage difference across thefirst electrode and the second electrode, and electrophoreticallydepositing the second material above the first electrode to form asecond layer, wherein the second layer has a second composition, asecond microstructure, and a second density, wherein at least one of:the first and second composition are different, the first and secondmicrostructure are different, and the first and second density aredifferent.

As shown in FIG. 1, an EPD device 100 may include a first electrode 110and a second electrode 106 positioned on either side of an EPD chamber118, with a voltage difference 116 applied across the two electrodes106, 110 that causes charged nanoparticles 102 and/or 104 in a solvent108 to move toward the first electrode 110 as indicated by the arrow. Insome embodiments, a substrate 112 may be placed on a solution side ofthe first electrode 110 such that nanoparticles 114 may collect thereon.

The EPD device 100, in some embodiments, may be used to depositmaterials to the first electrode 110 or to a conductive ornon-conductive substrate 112 positioned on a side of the electrode 110exposed to a solution 108 including the material 102, 104 to bedeposited. By controlling certain characteristics of formation ofstructures in an EPD process, such as the precursor material composition(e.g., homogenous or heterogeneous nanoparticle solutions) andorientation (e.g., non-spherical nanoparticles), deposition rates (e.g.,by controlling an electric field strength, using different solvents,etc.), particle self-assembly (e.g., controlling electric fieldstrength, particle size, particle concentration, temperature, etc.),material layers and thicknesses (e.g., through use of an automatedsample injection system and deposition time), and deposition patternswith each layer (e.g., via use of dynamic electrode patterning),intricate and complex structures may be formed using EPD processes thatmay include a plurality of densities, microstructures, and/orcompositions, according to embodiments described herein.

Equation 1 sets out the basic system-level model for electrophoreticdeposition, where W_(film) is the mass of the deposition layer, μ is theelectrophoretic mobility, E is the electric field, A is the area of theelectrode substrate, C is the deposition particle mass concentration,and t is the deposition time.W _(film)=∫^(t2) _(t1) μEACdt  Equation 1

Combining these principles with dynamic patterning and sample delivery(which is described in more detail later), electrophoretic depositionmay be employed to produce a diverse set of products with unique and/ordifficult to obtain shapes, designs, and properties custom-fitted to anyof a number of practical applications.

In one approach, EPD technology may be combined with pattern-orienteddeposition in order to effectuate complex two- and three-dimensionalpatterning structures. In another approach, coordinating sampleinjection during EPD further enables complex patterning of structuresthat may include concentration gradients of a deposited material incomplex two- and three-dimensional arrangements.

In another approach, multiple materials may be combined duringpatterning by way of coordinated sample injection in order to effectuatecomplex electrochemical and structural arrangements. By way of example,this approach may be employed to accomplish sample doping or to formceramics or composites, such as ceramic metals (cermets).

Similarly, multiple dynamic patterns may be overlaid in combination withdynamic sample injection during the EPD process to generate a layeredstructure having differing arrangements, densities, microstructures,and/or composition according to any number of factors, includingpreferences, application requirements, cost of materials, etc.

Now referring to FIGS. 2A-2C, according to one embodiment, a ceramic,metal, or cermet 200 comprises a first layer 202 having a gradient 206in composition, microstructure and/or density in an x-y plane orientedparallel to a plane of deposition of the first layer 202. The gradientof the first layer 202, according to various embodiments, may be smooth,abrupt, or comprised of small, incremental steps.

As shown in FIG. 2A, the x-y plane is represented in an isometric viewof a simplified schematic diagram of a single layer 202, which isrepresented by a plurality of white dots 210 and/or black dots 208. Thedots 210 and/or 208 may represent a density of the layer (such as theblack dots 208 representing a more dense volume, with the white dots 210representing a less dense volume), a composition of the layer (such asthe black dots 208 representing a first material, with the white dots210 representing a second material), a microstructure of the layer (suchas the black dots 208 representing a first lattice structure, with thewhite dots 210 representing a second lattice structure), etc. Of course,the embodiments described herein are not meant to be limiting on theinvention in any way. Also, the patterns are not limited to those shownin FIGS. 2A and 2B, and may include any shape (polygonal, regular,irregular, etc.), repeating pattern (single pixels, lines, shapes,areas, etc.), random array (e.g., a predefined composition of materialswith a random arrangement, such as a 25%/75% material A/material Bsplit, a 50%/50% material A/material B split, etc.), etc.

According to one embodiment, the gradient 206 of the first layer 202 maybe defined by a first material 208 being arranged in a first pattern anda second material 210 being arranged in a second pattern, wherein thefirst pattern is complementary to the second pattern. The term“complementary” indicates that one pattern does not overlay the otherpattern, but gaps may remain between the patterns where no material isdeposited, in some approaches. In other approaches, the second patternmay be a reverse or negative pattern of the first pattern, e.g., red andblack squares of a checker board. Of course, any pattern may be used forthe first and second patterns as would be understood by one of skill inthe art upon reading the present descriptions, including patterns thatare not complementary. In more approaches, the patterns may be changedas material is deposited, causing even more options to materialformation, layering, etc.

In another embodiment, at least the first material 208 and/or the firstlayer 202 may have a characteristic of being deposited through an EPDprocess according to the first pattern. This characteristic may include,in some embodiments, smooth, gradual gradients between the materials inthe first layer 202, abrupt transitions from the first material 208 tothe second material 210 in the first layer 202, regular patterningbetween the first material 208 and the second material 210, or any othercharacteristic of deposition through an EPD process as would beunderstood by one of skill in the art upon reading the presentdescriptions. In a further embodiment, at least the first material 208may have a characteristic of being deposited through the EPD processabove a non-planar electrode. For example, the non-planar electrode mayhave a cylindrical shape, a regular polygonal shape, a conical shape, acurved surface shape, or any other non-planar shape as would beunderstood by one of skill in the art upon reading the presentdescriptions. Non-planar electrodes are described in more detail later.

In another embodiment, the second material 210 may have a characteristicof being deposited through an EPD process, and may further have acharacteristic of being deposited above a non-planar electrode, asdescribed later. Moreover, this may include characteristics of thesecond material being deposited after the first material is deposited.

According to one embodiment, the ceramic, metal, or cermet 200 mayfurther comprise a second layer 204 above the first layer 202, whereinthe second layer 204 has a gradient in composition, microstructureand/or density in an x-y plane oriented parallel to a plane ofdeposition of the second layer 204. The gradient of the second layer204, according to various embodiments, may be smooth, abrupt, orcomprised of small, incremental steps.

In one embodiment, the gradient of the second layer 204 may be definedby the first material 208 being arranged in a third pattern and thesecond material 210 being arranged in a fourth pattern, wherein thethird pattern is complementary to the fourth pattern. Of course, thepatterns shown in FIGS. 2A and 2B are not limiting on the invention inany way, and any patterns may be used as would be understood by one ofskill in the art upon reading the present descriptions. In someapproaches, the first, second, third, and/or fourth patterns may overlayone another and/or be coexistent therewith.

In another embodiment, at least the first material 208, the secondmaterial 210 and/or the second layer 204 may have a characteristic ofbeing deposited through an EPD process according to the third pattern.In a further embodiment, at least the first material 208, the secondmaterial 210 and/or the second layer 204 may have a characteristic ofbeing deposited through the EPD process above a non-planar electrode, asdescribed previously.

In another embodiment, the first pattern may be different from the thirdpattern, e.g., each layer may use one or more unique pattern and/ormaterials, thereby creating a structure which, in the z-directionperpendicular to the x-y plane, may have differing arrangements ofmaterials. Of course, in another embodiment, the second pattern may bedifferent from the fourth pattern.

According to another embodiment, as shown in FIG. 2C, a gradient mayexist between the first layer 202 and the second layer 204 in az-direction perpendicular to the x-y plane of the first layer 202, thegradient being a transition from at least one of: a first composition, afirst microstructure, and a first density of the first layer 202 to atleast one of: a second composition, a second microstructure, and asecond density of the second layer 204, wherein at least one of: thefirst composition and the second composition are different, the firstmicrostructure and the second microstructure are different, and thefirst density and the second density are different. This gradient in thez-direction may be used in addition to or in place of a gradient in thex-y plane of each layer based on patterns, e.g., the ceramic, metal, orcermet 200 may be formed by changing solutions in an EPD chamber duringEPD processing, in one approach.

According to one proposed use, a high-powered laser may comprise theceramic 200 as a transparent ceramic optic in the laser.

As would be understood by one of skill in the art upon reading thepresent descriptions, one or more additional layers may be arrangedabove the first layer 202 and the second layer 204, thereby forming astructure that may have complex layering and/or composition, withgradients possible in the x-y plane and the z-direction across all thelayers.

In one embodiment, EPD may be used in conjunction with controlledelectric field patterns to direct the composition of deposited materialin an x-y plane parallel to a plane of deposition, including multilayerdeposition of a single pattern as well as dynamically changing patternsas the particles build up in the z-dimension, perpendicular to the x-yplane. This technique enables, for example, transparent ceramic opticswith a controlled, smooth, x-y concentration of dopant material.

Current optics designs are material and process limited to uniformcomposition profiles across optical components and laser gain media. Todate, only coarse step function composition changes have been producedin the most advanced transparent ceramic optics. However, in oneembodiment, because the electrophoretic deposition occurs only where thefield is applied, precisely patterned x-y concentration profiles arepossible by modifying the electrode pattern in this plane. To enablethis capability, one electrode in a typical EPD system may be replacedwith a photoconductive layer (such as α-H:Si) and a transparent orsemi-transparent electrode, e.g., of indium tin oxide (ITO) andilluminated in specific regions using any number of light sources and/orlight altering devices or mechanisms, such as a static mask, a dynamicpattern from a light altering or emitting mechanism, etc.

With reference to FIG. 3A, an EPD device 300 is shown according to oneembodiment. The EPD device 300 comprises a first electrode 110 and asecond electrode 106 positioned on either side of an EPD chamber 118. Acircuit is provided to apply a voltage difference 116 across the twoelectrodes 106, 110. The EPD chamber 118 includes a solution which maycomprise a solvent 108 (either aqueous or organic) and one or morematerials 102 and/or 104 therein for deposition. In some embodiments, asubstrate 112 may be placed on a solution side of the first electrode110 such that the materials 114 may collect thereon.

Referring to FIG. 3A, a light source 304 may be provided to providelight 308 to a photoconductive layer 306 that becomes conductive inresponse to areas where the light 308 is shined thereon. In thisapproach, the first electrode 110 may be transparent orsemi-transparent, thereby allowing light 308 from the light source 304to reach the photoconductive layer 306. In FIG. 3A, the substrate 112does not extend to fully cover the photoconductive layer 306, but theinvention is not so limited. In this or any other embodiment, thephotoconductive layer 306 may be applied to the substrate 112, to thefirst electrode 110, may be a separate component in the device 300, maybe shaped differently or the same as any other component to which it isapplied, etc.

As shown in FIG. 3A, the light 308 from the light source 304, in oneembodiment, passes through a light altering mechanism 302, which mayinclude one or more lenses or optical devices, one or more mirrors, oneor more filters, one or more screens, or any other light alteringmechanism as would be known to one of skill in the art that would becapable of providing one or more patterns to the light 308 (e.g., toalter the light 308 from the light source 304) prior to reaching thephotoconductive layer 306, in various embodiments. In some embodiments,the light altering mechanism 302 may be capable of dynamically alteringthe light 308, according to user preferences, applications requirements,predefined patterns, spacings, durations, etc. According to someembodiments, light altering mechanism 302 may include a digital lightprocessing (DLP) chip, laser scanning, light rastering, and/or a liquidcrystal on silicon (LCoS) chip or array.

As shown in FIG. 3B, the EPD chamber 118 is essentially the same as inFIG. 3A, except that in FIG. 3B, the light altering mechanism 310 ispositioned near to the photoconductive layer 306. Therefore, the light308 from the light source 304, in one embodiment, passes through thelight altering mechanism 310 prior to reaching the photoconductive layer306, in one embodiment. According to several approaches, the lightaltering mechanism 310 may include a LCoS array, one or more filters,one or more patterned screens, or any other light altering mechanism aswould be known to one of skill in the art that would be capable ofproviding one or more patterns to the light 308 (e.g., to alter thelight 308 from the light source 304).

In these embodiments, dynamic altering of the light 308 is greatlyenhanced, as the light altering mechanism may be programmed to changeover time to allow light 308 to reach the photoconductive layer 306 asdesired by a user.

The light source 304 may be any light source capable of providingsufficient light 308 to shine upon designated areas of thephotoconductive layer 306, as would be understood by one of skill in theart upon reading the present descriptions.

Other components shown in FIGS. 3A-3B of the EPD devices 300, 350 notspecifically described herein may be chosen, selected, and optimizedaccording to any number of factors, such as size limitations, powerrequirements, formation time, etc., as would be known by one of skill inthe art.

Now referring to FIG. 4, a method 400 for forming a ceramic, metal, orcermet is shown according to one embodiment. The method 400 may becarried out in any desired environment, including those shown in FIGS. 1and 3A-3B, among others.

In operation 402, light in a first pattern is provided to aphotoconductive layer positioned near a transparent or semi-transparentelectrode of an EPD chamber.

As used herein in the various embodiments, the “transparent” electrodemay be or semi-transparent or semi-transparent as would be understood byone of skill in the art, the photoconductive layer is positioned betweenthe transparent electrode and a second electrode, and portions of thephotoconductive layer become conductive in response to the lightaccording to the first pattern, in one embodiment.

In operation 404, a voltage difference is applied across the transparentelectrode and the second electrode. Any method may be used for applyingthe voltage difference to form an electric field that causes chargedparticles in the solution, such as a first material, to move toward anoppositely charged electrode. For sake of simplicity, in thisdescription, the charged particles always migrate toward the transparent(first) electrode.

In operation 406, a first material is electrophoretically depositedabove the photoconductive layer according to the first pattern, whereinthe EPD chamber comprises an aqueous or organic solution having thefirst material to be deposited therein.

In one embodiment, the method 400 further comprises the followingoptional operations.

In optional operation 408, an aqueous or organic solution having asecond material is introduced into the EPD chamber.

In optional operation 410, light in a second pattern is provided to thephotoconductive layer, wherein portions of the photoconductive layerbecome conductive in response to the light according to the secondpattern.

In optional operation 412, a voltage difference is applied across thetransparent electrode and the second electrode. This second voltagedifference may be the same or different from that in operation 404,e.g., to adjust a rate of deposition.

In optional operation 414, the second material is electrophoreticallydeposited above the photoconductive layer according to the secondpattern to form a first layer that is comprised of the first and secondmaterials. The first and second patterns direct deposition of the firstand second materials to form a gradient in composition, microstructureand/or density in an x-y plane oriented parallel to a plane ofdeposition of the first layer.

In one embodiment, the first pattern and/or the second pattern may bedynamically altered to modify a gradient in composition, microstructureand/or density in a z-direction across a plurality of layers, whereinthe z-direction is perpendicular to the x-y plane of the first layer.

In a further embodiment, a gradient may exist in a z-directionperpendicular to the x-y plane between the first layer and a secondlayer formed above the first layer, the gradient being a transition fromat least one of: a first composition, a first microstructure, and afirst density of the first layer to at least one of: a secondcomposition, a second microstructure, and a second density of the secondlayer.

According to another embodiment, the first pattern and the secondpattern may be complementary to each other, as discussed previously.

In another embodiment, the method 400 may further comprise expelling theaqueous or organic solution having the first material from the EPDchamber prior to introducing the aqueous or organic solution having thesecond material into the EPD chamber. In this way, more abrupttransitions from the electrophoretically deposited first material to theelectrophoretically deposited second material may be made, whereasslowly introducing the second material (such as in a solution having thesecond material therein) into the EPD chamber while the first solutionis still present may result in more gradual transitions from the firstmaterial to the second material in the ceramic, metal, or cermet.

According to one approach, the first and second patterns may cause thefirst layer to have a gradual gradient shift in composition,microstructure, and/or density in the x-y plane of the first layer,e.g., the gradient change varies across the first layer in the x-yplane, perhaps smoothly, abruptly, in small incremental steps, etc., aswould be understood by one of skill in the art upon reading the presentdescriptions. In one approach, the pattern may gradually be shifted fromthe first pattern to the second pattern to form a smooth, gradualgradient in the layer.

In another approach, the transparent electrode may have a non-planarshape, e.g., it is cylindrical, polygonal, conical, etc., as will bedescribed in more detail in reference to FIG. 8.

According to another embodiment, field-aligned EPD may be used to alignnano-rod and/or micron-scale rod particles (non-spherical particleshaving a longitudinal length greater than a width) of a non-cubicmaterial as they are deposited to form a green structure. In general,the longitudinal axes of the particles become aligned with each other inthe electric field extending across the EPD chamber. See, e.g., FIG. 5B,discussed below. This technique can produce transparent ceramicscomposed of a non-cubic material. Laser physicists and optical systemengineers are currently hindered by the small subset of materialsavailable for their designs. The only crystalline materials available tothem are those that can be grown as single crystals and isotropic cubicmaterials which can be formed into transparent ceramics. By depositingnano-rods and/or micron-scale rods of a non-cubic material in the sameorientation, the resulting green-body may be sintered to a transparentceramic.

This approach may use very strong magnetic fields (on the order of 10Tesla) to align particles. Micro- and nano-rod and/or micron-scale rodparticles align with their longitudinal axes parallel to an appliedelectric field (and thus, substantially parallel to each other) due todielectrophoretic and induced charge electrophoretic motion. Sinceelectric dipoles are more readily induced in ceramic materials thanmagnetic dipoles, this method is more effective using EPD. In the EPDsystem, the nano-rods and/or micron-scale rods align in the electricfield in suspension and retain their alignment as they are deposited onthe surface.

Now referring to FIGS. 5A-5B, a ceramic 506, particularly a transparentceramic, and a method of forming the ceramic 506 are shown according tovarious embodiments. FIG. 5A shows a condition when an electric field isnot activated, and FIG. 5B shows a condition when the electric field isactivated for a time.

Referring again to FIGS. 5A-5B, in one embodiment, the ceramic 506comprises a plurality of layers 504 comprising particles 502 of anon-cubic material (e.g., the particles have a non-spherical shape, anon-cubic shape, etc., and do not readily form into crystal lattices).Each layer 504 is characterized by the particles 502 of the non-cubicmaterial being aligned in a common direction, as indicated by the arrowin FIG. 5B when the electric field 116 is activated. According to apreferred embodiment, after sintering, curing, or any other process tocreate a ceramic or composite from the green structure shown in FIG. 5B,the ceramic may be transparent, which is difficult to achieve fromnon-cubic starting materials.

According to one embodiment, the plurality of layers 504 may have acharacteristic of being deposited through an EPD process, as describedpreviously. In a further embodiment, the plurality of layers 504 mayhave a characteristic of being deposited through the EPD process above anon-planar electrode, as will be described later in more detail.

In one approach, the starting materials, e.g., the non-cubic materialcomprises a plurality of particles 502, e.g., nano-rod and/ormicron-scale rod particles having a longitudinal length that is at leastthree times longer than a width thereof, as shown in FIGS. 5A-5B.

In one preferred use, a high-powered laser may comprise the ceramic 506(after sintering, curing, etc., thereof) as a transparent ceramic opticin the laser.

In another embodiment, non-spherical particles may be aligned within anelectrophoretic field using the direct current (DC) electrophoreticfield and/or an alternating current (AC) electric field appliedperpendicular to a plane of deposition. In this approach, upondeposition, the non-spherical particles may form a structure with highlyaligned grains. In some embodiments, highly aligned grains orientationmay reduce differential indices of refraction between grains, thusrendering useful optical properties to the aligned structures.

For example, a method for forming a ceramic, particularly a transparentceramic, from non-cubic starting material is described that may becarried out in any desired environment, including those shown in FIGS. 1and 3A-3B, among others.

In one embodiment, a plurality of layers 504 of particles 502 of anon-cubic material are electrophoretically deposited as describedpreviously. The particles 502 of the deposited non-cubic material areoriented in a common direction, as indicated by the arrow. The commondirection may be related to a longitudinal direction of the particles502, e.g., length of a cylinder, length of a rectangular polygon, etc.

The method may further comprise applying an alternating current (AC)electric field in a direction parallel to a plane of deposition of theplurality of layers, which is also parallel to a direction of a DC fieldapplied during EPD, according to one embodiment.

In another embodiment, the method may further comprise sintering theplurality of layers of non-cubic material 506 to form a ceramic, whereinthe non-cubic material is selected such that the ceramic is transparent.

In one approach, the plurality of layers may be deposited above anon-planar electrode, as discussed in detail later.

In one embodiment, non-cubic crystalline materials, such ashydroxyapotite, chloroapotite, alumina, etc., may be formed into crystalstructures exhibiting optical properties of highly cubic structures. Inthis approach, non-spherical particles may be aligned and deposited in acrystal structure and possibly mixed with dopants during deposition soas to generate a smooth gradient of crystalline material with preciselyknown optical characteristics.

One advantage of the above described AC-EP alignment—and DC-EPD methodis a significant reduction in production time for highly aligned opticalcrystals, whereas conventional single crystal growing methods may takeseveral days to months to produce an aligned crystal of sufficient sizefor desired application, the same size and quality crystal may begenerated in a matter of hours by utilizing EP alignment and deposition.

In one approach, a conductive base material such as a metal electrodemay serve as a substrate for plating subsequent layers of material incomplex structures defined by pattern-oriented deposition.

In another approach, a metal electrode may be replaced by a transparentor semi-transparent electrode with an attached photoconductive layercapable of being illuminated in specified regions using either a staticmask or dynamic pattern from a dynamic light processing (DLP) chip,liquid crystal on silicon (LCoS), or other similar device as known inthe art.

In yet another approach, a nonconductive substrate may be coated with athin film of conductive material, such as gold, nickel, platinum, etc.,as known in the art, in order to confer conductivity on the substrateand allow non-planar deposition thereupon. In this manner, virtually anysubstrate may be subjected to specialized modification and coating usingthe EPD methodology.

In another embodiment, EPD may be used with automated particle injectionto control z-axis deposition and composition of a suspension solution.This technique enables production of multicomposition materials, such asopaque ceramic armor prototypes with a gradient in the properties in thez-direction from a hard strike face (boron carbide) to ductile backing(aluminum).

To control the composition of the green-body in the z-axis, thecomposition of the suspension may be adjusted in the EPD chamber usingan automated injection system, as shown in FIG. 6, according to oneembodiment. Using this technique, a sharp gradient may be formed byabruptly changing the particle solution or a smooth gradient bygradually adjusting between two particle types. Of course, more than twoparticle types may be used in any embodiment, and gradients between two,three, four, or greater materials may be formed using techniquesdescribed herein.

For the armor application, particles of a hard material such as AlMgB₁₄,TiB₂, SiC, boron carbide, etc. particles may be electrophoreticallydeposited to create a hard surface, then the solution may gradually betransitioned to include an increasing amount of relatively lightermetals or alloys such as particles of aluminum, Al—Mg, Al—Mg—Li, etc. tocreate a ductile backing. This transition from hard to ductile materialis predicted to be an ideal composition for an efficient armor plate, asopposed to a sharp gradient.

Now referring to FIG. 6, a ceramic, metal, or cermet 610 is shown beingformed using an EPD device 600 comprising an EPD chamber 118 and anautomated injection system 602, according to one embodiment. Optionally,the light source 304 and accompanying light altering mechanism 306 maybe included, as previously described.

The automated injection system 602, according to one embodiment, mayinclude a pump 604, a controller 608 for controlling pump operation andparticle selection, and power 606 for each component. As shown in FIG.6, there are six particle types to choose from; however, the inventionis not so limited, and any number of particle types, concentrations,sizes, etc., may be available for injecting into the EPD chamber 118,according to various embodiments.

According to one embodiment, the ceramic, metal, or cermet 610 comprisesa first layer 612 having a first composition, a first microstructure,and a first density and a second layer 614 above the first layer 612,the second layer 614 having at least one of: a second composition, asecond microstructure, and a second density. A gradient exists betweenthe first layer 612 and the second layer 614, and the first and secondlayers 612, 614 have a characteristic of being formed in an EPD chamber,as previously described.

In one embodiment, the gradient may be a transition from at least oneof: the first composition, the first microstructure, and the firstdensity, to the at least one of: the second composition, the secondmicrostructure, and the second density. That is to say, any of thecomposition, microstructure and/or density may change from the firstlayer 612 to the second layer 614, with any of the remaining propertiesbeing the same, according to various embodiments.

For example, and not meant to be limiting on the invention in any way, abody centered cubic (bcc) structure having a density of about 4.5 g/cm³may include a first layer having a composition of about 60% O and 40% Alin a face centered cubic (fcc) structure and a density of about 4 g/cm³,and a second layer having a composition of about 50% O and 50% Al—. Inthis example, all three properties changed from the first layer to thesecond layer, but this is not required as the gradient may affect onlyone property, two properties, all three properties or even otherproperties, such as melting point, freezing point, conductivity,rigidity, or any other mechanical property, chemical property,electrical property, optical property, etc., as would be understood byone of skill in the art upon reading the present descriptions.

In another embodiment, the gradient from the first layer 612 to thesecond layer 614 may be abrupt, gradual, in small incremental steps,etc., as would be understood by one of skill in the art upon reading thepresent descriptions.

According to another embodiment, the first layer 612 and the secondlayer 614 may have a characteristic of being deposited above anon-planar electrode, as is described in more detail later.

In a preferred use, the ceramic, metal, or cermet 610 (after sintering,curing, etc.) may be used in an armor system as one of a plurality ofarmor plates. In this or any other embodiment, the first layer 612 maycomprise a relatively harder, heavier material and the second layer 614may comprise a relatively lighter material, among other rigid/flexiblearmor arrangements.

Now referring to FIGS. 6-7, a method 700 for forming a ceramic, metal,or cermet is shown according to one embodiment. The method 700 may becarried out in any desired environment, including those shown in FIGS.1, 3, and 6, among others. FIG. 6 is used to refer to components of theEPD device 600 according to various embodiments, and in FIG. 6, thefirst two layers 612, 614 of the ceramic, metal, or cermet 610 have beenformed, and therefore the formation of the first layer 612 cannot bedescribed in complete detail with reference to FIG. 6, but progressessimilarly to that of the second layer 614, in some approaches.

In operation 702, an EPD device 600 is provided. The EPD device 600comprises an EPD chamber 118, a first electrode 110 positioned at an endof the EPD chamber 118, and a second electrode 106 positioned at anopposite end of the EPD chamber 118.

In operation 704, a first solution is provided to the EPD chamber 118using an automated injection system 602, the first solution comprising afirst solvent and a first material 102.

In operation 706, a voltage difference 116 is applied across the firstelectrode 110 and the second electrode 106.

In operation 708, the first material 102 is electrophoreticallydeposited above the first electrode 110 to form a first layer 612,wherein the first layer 612 has a first composition, a firstmicrostructure, and a first density.

In operation 710, a second solution is introduced to the EPD chamber 118using the automated injection system 602, the second solution comprisinga second solvent 616 and a second material 104.

In operation 712, a voltage difference 116 is applied across the firstelectrode 110 and the second electrode 106.

In operation 714, the second material 104 is electrophoreticallydeposited above the first electrode 110 (and possibly the first material102) to form a second layer 614, wherein the second layer 614 has asecond composition, a second microstructure, and a second density.

At least one of: the first and second composition are different, thefirst and second microstructure are different, and the first and seconddensity are different, thereby defining different layers of the ceramic,metal, or cermet 610.

According to some embodiments, optional operations may be performed inaddition to those in method 700. For example, in one approach, light 308in a first pattern may be provided to a photoconductive layer 306positioned near the first electrode 110, wherein the first electrode 110is transparent or semi-transparent and the photoconductive layer 306 ispositioned between the first electrode 110 and the second electrode 106.Portions of the photoconductive layer 306 become conductive in responseto the light 308 according to the first pattern, and the first material102 is electrophoretically deposited above the photoconductive layer 306according to the first pattern.

In another embodiment, light 308 in a second pattern may be provided tothe photoconductive layer 306 after introducing the second solution tothe EPD chamber 118, wherein portions of the photoconductive layer 306become conductive in response to the light 308 according to the secondpattern, the second material 104 is electrophoretically deposited abovethe photoconductive layer 306 according to the second pattern, and thefirst and second patterns direct deposition of the first 102 and secondmaterials 104 to form a gradient in composition, microstructure and/ordensity in an x-y plane oriented parallel to a plane of thephotoconductive layer 306, e.g., a plane positioned perpendicular to adirection of movement of the particles caused by the voltage difference116.

According to one embodiment, the first pattern and/or second pattern maybe dynamically altered to modify a gradient in composition,microstructure and/or density in a z-direction across a plurality oflayers, wherein the z-direction is perpendicular to the x-y plane.

In another embodiment, the first electrode 110 may have a non-planarshape, as described later.

In one approach, the first solvent and the second solvent may be thesame and the first 102 and second materials 104 may be different, or inan alternate approach, the first solvent and the second solvent may bedifferent and the first 102 and second materials 104 may be the same.The solvent may be used to control the deposition rate of the materialstherein, according to some embodiments.

In another embodiment, a gradient exists between the first layer 612 andthe second layer 614, the gradient being a transition from the firstcomposition, the first microstructure, and the first density, to thesecond composition, the second microstructure, and the second density.

According to one approach, the gradient from the first layer 612 to thesecond layer 614 may be abrupt, gradual, comprise small incrementalsteps, etc.

In several embodiments, the first and second composition may be thesame, the first and second microstructure may be the same, and/or thefirst and second density may be the same; however, as previouslydescribed, each may be different in other embodiments.

According to one approach, the method 700 may further comprise expellingthe first solution from the EPD chamber 118 prior to introducing thesecond solution to the EPD chamber 118.

In further approaches, the first electrode may have a non-planar shape,as will be described later.

According to one approach, the first layer 612 may comprise boroncarbide and the second layer 614 may comprise aluminum, or some othercombination of rigid and flexible materials as would be understood byone of skill in the art.

In another embodiment, as referenced throughout, EPD with shapedgraphite or machined metal electrodes with non-planar geometries may beused to create green-bodies with complex shapes. This technique can becombined with any of the previously described techniques tosimultaneously achieve a defined nano- or microstructure. Potentialapplications include opaque ceramic armor prototypes with a radius ofcurvature greater than about 2 inches made from a single precursormaterial. Using graphite as an electrode material, complex electrodegeometries may be created which provide a contour for the bulk partduring deposition. Using finite element modeling as a guide, theelectrode shapes and the resulting electric fields may be controlledsuch that they are conducive to rapid and dense deposition of material.

FIGS. 8A-8C show electrode configurations for EPD, according to variousembodiments. In FIG. 8A, an EPD device is shown with a non-planarelectrode configuration. As can be seen, the first electrode 802 extendsfrom an end of the EPD chamber 118, while the second electrode 804 ispositioned apart from the first electrode 802 at a substantially equaldistance, thereby providing an electric field to cause deposition when avoltage difference is applied across the electrodes 802, 804. In this orany other embodiment, the first electrode 802 may have a circularprofile, a polygonal profile, a curved profile, etc. The shape of thefirst electrode 802 may be chosen to correspond to a desired shape ofthe deposited material and subsequent structure formed therefrom in someembodiments. In some embodiments, as shown in FIG. 8A, a layer 814 maybe positioned between the first electrode 802 and the second electrode804, which may be a conductive layer, a substrate, a coating, etc., aspreviously described.

Now referring to FIG. 8B, the first electrode 806 may comprise a curvedsurface according to one embodiment, with the second electrode 808 beingpositioned at substantially a constant distance apart, thereby providinga more uniform electric field upon application of a voltage differencebetween the electrodes 806, 808. The first electrode 806 may have acontinuously curved surface, or may have portions thereof that arecurved, with other portions planar or flat, according to variousembodiments.

As shown in FIG. 8C, according to another embodiment, the firstelectrode 810 may have a conical surface, which may have a circular orpolygonal profile, with the second electrode 812 being positioned atabout a constant distance apart.

Of course, FIGS. 8A-8C are exemplary electrode configurations, and anycombination of curved, flat, circular, polygonal, or any other shape asknown in the art may be used for electrode design, particularly in anattempt to adhere to application requirements, as described herein. Theinvention is not meant to be limited to the electrode configurationsdescribed herein, but may include electrode configurations of any typeas would be understood by one of skill in the art upon reading thepresent descriptions. For example, deposition may be performed onto thereverse electrodes 804 (FIG. 8A), 808 (FIG. 8B), 812 (FIG. 8C),respectively.

As the embodiments described herein aptly demonstrate, the EPD methodsand structures formed through the EPD methods disclosed herein,according to various embodiments, may be used for any number of novelmaterials and structures. According to some embodiments, the structuresand methods may be used for applications including: 1) fabricatingtransparent ceramic optics with doping profiles tailored inthree-dimensions to enable new high-powered laser designs; 2) depositingaligned particles of non-cubic ceramics to create a new family oftransparent ceramics; 3) creating ceramic or cermet armor plates withcomplex geometries and controlled material composition for lightweightand highly effective armor designs, etc.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only, and notlimitation. Thus, the breadth and scope of a preferred embodiment shouldnot be limited by any of the above-described exemplary embodiments, butshould be defined only in accordance with the following claims and theirequivalents.

What is claimed is:
 1. A product, comprising: a first layer comprising afirst material, the first layer having a gradient in composition,microstructure and/or density in an x-y plane, and the x-y plane beingoriented parallel to a plane of deposition of the first layer; whereinthe first material includes non-spherical particles; and wherein theproduct is optically transparent.
 2. The product as recited in claim 1,wherein the first layer comprises the first material arranged in a firstpattern.
 3. The product as recited in claim 1, wherein the firstmaterial is deposited above a non-planar electrode.
 4. The product asrecited in claim 1, further comprising a second layer above the firstlayer, wherein the second layer has a second gradient in composition,microstructure and/or density in the x-y plane.
 5. The product asrecited in claim 4, wherein the second layer comprises a second materialand/or the first material arranged in a second pattern.
 6. The productas recited in claim 4, wherein the second gradient is defined by thefirst material being arranged in a third pattern within the secondlayer, and a second material being arranged in a fourth pattern withinthe second layer; wherein the third pattern is complementary to thefourth pattern; wherein the first material is arranged in a firstpattern in the first layer; and wherein the first pattern is differentfrom the third pattern.
 7. The product as recited in claim 4, wherein athird gradient exists between the first layer and the second layer in az-direction perpendicular to the x-y plane of the first layer, the thirdgradient being from: a first composition, a first microstructure, and/ora first density of the first layer to: a second composition, a secondmicrostructure, and/or a second density of the second layer.
 8. Theproduct as recited in claim 7, wherein the third gradient is defined bya series of discrete, incremental steps.
 9. The product as recited inclaim 7, wherein the third gradient is defined by a smooth transitionfrom the first composition, the first microstructure, and/or the firstdensity of the first layer to the second composition, the secondmicrostructure, and/or the second density of the second layer.
 10. Theproduct as recited in claim 7, wherein at least one of the followingprovisos is satisfied: the first composition and the second compositionare different; the first microstructure and the second microstructureare different; and the first density and the second density aredifferent.
 11. A ceramic, comprising: a plurality of layers comprisingnon-spherical particles of a non-cubic material, wherein thenon-spherical particles are characterized by a longitudinal length thatis at least three times longer than a width of the non-sphericalparticles, and wherein each layer is individually characterized by thenon-spherical particles thereof being aligned in a common direction. 12.The ceramic as recited in claim 11, wherein the plurality of layers aredeposited above a non-planar electrode.
 13. The ceramic as recited inclaim 11, wherein the ceramic is transparent.
 14. The product as recitedin claim 1, further comprising a second layer above the first layer,wherein the product is functionally graded in three dimensions.